Code division multiple access (CDMA) is a digital wireless technology that inherently has relatively greater bandwidth capacity, i.e., that inherently permits the servicing of more telephone calls per frequency band, than other wireless communication technologies. Moreover, the spread spectrum principles of CDMA inherently provide secure communications. U.S. Pat. No. 4,901,307, incorporated herein by reference, sets forth details of a CDMA system, which can be used to transmit both voice calls and non-voice computer data.
Despite the advantages of CDMA, other wireless systems exist that use other principles. For example, in much of the world GSM is used, which employs a version of time division multiple access.
Whether CDMA principles or other wireless principles are used, wireless communication systems can be thought of as having two main components, namely, the wireless radio access network (RAN) and the core infrastructure which communicates with the RAN and with external systems, such as the public switched telephone network (PSTN), the Internet (particularly although not exclusively for data calls), etc. The core infrastructures associated with the various wireless technologies can be very expensive, both in terms of hardware and in terms of developing communication protocols to support particularized, typically system-specific call switching, subscription and attendant authentication and call monitoring, and billing. Consequently, the communication protocols of one wireless system (in the case of GSM, GSM protocols, and in the case of CDMA such as cdma2000-1x, IS-41 protocols) may not be compatible with those of another system without expensively prohibitive alterations in the core infrastructure of one system or the other.
From the disclosure above, the present invention recognizes that it would be desirable to enable the use of a CDMA-based RAN, with its attendant advantages, with a GSM-based core infrastructure, because GSM is extant in much of the world. The present invention still further recognizes, in light of the above, the desirability of minimizing if not eliminating the need to modify the communication protocols of the GSM core infrastructure.
Of particular focus in the present invention is the transport of non-voice computer data from a mobile station (MS) to a core infrastructure. In a CDMA system the MS can be a telephone, laptop computer, or other CDMA device that communicates digital data over the CDMA wireless RAN to a CDMA core infrastructure, which includes a packet data serving node (PDSN) that conveys the data to, e.g., the Internet using packet data call procedures that are part of the IS-41 protocols. In a GSM system the MS conveys digital data over the GSM RAN to a GSM core infrastructure. Until GSM begins deployment of so-called wideband CDMA, and even afterward for those service providers who will not be able to use wideband CDMA because of frequency spectrum limitations, the computer data transmission portion of the GSM infrastructure will continue to be a so-called GPRS infrastructure. The GPRS computer data infrastructure includes, for each base station system (BSS) of the GSM RAN, a corresponding serving GPRS service node (SGSN) coupled to a central gateway GPRS service node (GGSN). The SGSN and GGSN cooperate to convey the computer data using GSM protocols. The problem addressed by the present invention is how to transmit computer data using a CDMA RAN in combination with a GSM core infrastructure, without requiring excessive modifications to the GSM core infrastructure.